Metabolic control of diabetes, measured by hemoglobin A1c (HbA1c), reduces the risk of microvascular complications. Health care providers frequently do not meet standards for managing HbA1c and individuals with diabetes are often not aware of their HbA1c values. To address these issues and reduce population- attributable risk due to elevated HbA1c, the New York City Department of Health and Mental Hygiene (DOHMH) developed an innovative HbA1c registry, which requires all major laboratories to report HbA1c results electronically. We propose to utilize this registry to conduct a randomized controlled trial addressing the following specific aims: 1) to evaluate the incremental effect of a tiered and tailored, patient-centered telephone intervention, in English and Spanish, on the mean HbA1c levels beyond that achieved with print materials mailed to patients and providers by the DOHMH registry intervention;2) determine what patient demographic and psychosocial factors mediate the effect of the interventions;and 3) provide estimates of implementation costs of the tiered, tailored telephone intervention for comparison with the print intervention. The individual is the unit of sampling, assignment and analysis. After eligibility is assessed and informed consent is obtained by telephone, the individual will be randomly assigned to one of the two groups. The patient telephone intervention will focus on collaborative problem solving for resolving barriers to medication adherence, improving lifestyle behaviors, and communicatiing effectively with their providers. The print materials from the DOHMH will communicate HbA1c results to patients and their providers, with strategies to improve them. The study outcome will be change in HbA1c values from the registry records from baseline to one-year post-randomization. A total of 941 individuals with diabetes will be needed to provide 83% power to detect a statistically significant difference (p<0.05) between groups of at least 0.3% in absolute HbA1c. Psychosocial data on depression, health behaviors, and risk perceptions will be collected by telephone. Intervention cost data will be evaluated for translation of findings and scalability. At study end, we will know the extent to which this intervention will improve metabolic control in a low-income, multi-ethnic sample who are part of the DOHMH HbA1c registry in the South Bronx, New York. These findings will inform public health policies and practices in New York City, as well as other urban areas throughout the nation.